1. Field of the Invention
The invention relates to downhole positive displacement rotary motors of the type used for drilling operations.
2. Description of the Related Art
Linear downhole motors are widely known in the field of drilling operations. Motors are used to develop rotational drive on drilling implements from the drilling fluids forced through the drilling string. Typically, prior art motors use varying configurations of stator and rotor systems. Some examples of prior art systems follow:
U.S. Pat. No. 3,088,529 issued to Cullen et al. on May 7, 1963, discloses a cylindrical fluid-driven downhole engine having a central shaft possessing multiple rotors with moveable vanes contained in shaped stators in a linear casing that produce rotary motion in the shaft and attachable tools when fluid is forced through the casing configuration to sequentially push against vanes of the rotor.
U.S. Pat. No. 3,838,953 issued to Peterson on Oct. 1, 1974 discloses a cylindrical downhole rotor-stator motor, driven by a recirculating hydraulic system creating force against the rotor vanes independent of the fluid flushing system.
U.S. Pat. No. 3,876,350 issued to Warder on Apr. 8, 1975 discloses a positive displacement hydraulic-driven machine having fluid passages axially traveling the length of a central rotor shaft, providing inlet and outlet flow to multiple annular chambers defined by moveable linear vanes, a circumferential stator and a rotor. The device also employs a dumping valve, which continues to discharge fluid when stalling occurs.
U.S. Pat. No. 4,105,377 issued to Mayall on Aug. 8, 1978 discloses a hydraulic downhole roller motor wherein a core rotor possesses multiple external axial slots, wherein rod roller vanes are alternatingly compressed and withdrawn by forces of a shaped cylindrical housing and directed fluid flow, producing rotary motion in the core rotor and attachable tools.
U.S. Pat. Nos. 5,518,379, 5,785,509 and 5,833,444 issued to Harris et al. on May 21, 1996, Jul. 28, 1998 and Nov. 10, 1998, respectively, disclose variations of a fluid-driven downhole motor having a tubular rotor, with a central flow channel and radial, flow channels to direct the fluid to at least one action chamber between hollow tube stator and the tubular rotor, wherein the fluid acts on rolling vane rods, recessible in wells in the interior surface of the stator, producing rotary motion.
U.S. Pat. No. 6,302,666 B1 issued to Grupping on Oct. 16, 2001 discloses a roller vane motor for downhole drilling, wherein the housing is internally shaped to release and depress the roller vanes within wells in the rotor, producing rotation when fluid is forced through the housing.
It would be an improvement to the field to provide a fluid motor that produces rotational motion from reciprocation of multiple double-action piston sleeves by controlled application of hydraulic pressure to the ends of each piston sleeve. It would also be an improvement for a fluid motor to employ hydraulic energy of a fluid while preserving energy needed for other purposes in an application. It would also be an improvement for a fluid motor to be operable with either or both compressible and non-compressible fluids. It would also be an improvement to the field for a device to be adaptable to produce an output torque curve with simple design modifications.